[BUG] [Experimental] Runtime values in tags and sku #3884

Existing rule

No response

Description of the issue

Originally reported microsoft/PSRule#3425

When using the new experimental feature in Bicep from 0.46.1: https://github.com/Azure/bicep/releases
([Experimental] Runtime values in tags and sku)

resource example 'Microsoft...' = {
   name: 'example'
   location: resourceGroup().location
   sku: {
      name: this.existingResource().?sku.name ?? 'Standard'
   }
   tags: this.existingResource().?tags ?? {}
}

Error messages

Exception calling "GetBicepParamResources" with "2" argument(s): "Unable to expand resources because the source file '/home/vsts/work/1/s/main.bicep' was not valid. The deployment 'root/2026-08-07_14.45' with symbolic name 'hubResourceGroup' failed. An error occurred evaluating expression '[if(parameters('keepExistingTags'), union(coalesce(tryGet(target('full'), 'tags'), createObject()), parameters('tags')), parameters('tags'))]' line 701 at path 'tags'. The function "target" was not found."

Reproduction

Create a bicep file containing the new function:

resource example 'Microsoft...' = {
   name: 'example'
   location: resourceGroup().location
   sku: {
      name: this.existingResource().?sku.name ?? 'Standard'
   }
   tags: this.existingResource().?tags ?? {}
}

Version of PSRule

2.9.0

Version of PSRule for Azure

No response

Additional context

Azure DevOps Microsoft Hosted Agent using the latest version of Linux, running in a PowerShell task using the latest version of bicep (0.46.1)